An azimuth sensor (geomagnetic sensor) measures an azimuth by detecting a direction of geomagnetism. However, geomagnetism to be measured is very weak. Thus, in order to precisely detect an azimuth, it is necessary to detect a real geomagnetism by canceling an offset resulting from a magnetic field that is present in a surrounding environment (magnetic field generated within a set mounted with an azimuth sensor, a magnetic field generated by a powerful magnet placed around an azimuth sensor, or the like), or an offset resulting from the performance of an azimuth sensor itself.
An offset of an azimuth sensor is continuously changed temporally and spatially. Thus, in order to precisely detect an azimuth, it is required to quickly and continuously cancel an offset of the azimuth sensor.
An offset correction method includes a method for manually correcting an offset by a user who uses it on purpose and a method for automatically correcting an offset without a manual input from the user. Between the manual correction and the automatic correction, in consideration of enhancing the user convenience or detection precision of an azimuth sensor, it is preferable to employ the latter method.
In this regard, there was a prior method for automatically correcting an offset without a manual input from the user.
However, in this prior method, a large amount of operation is required to process the offset correction, and thus, in order to quickly and continuously cancel an offset, a high level of operation capability is required.